Pug mill attack of titaniferous ores



Nov. 2, 1937.

v F. H. McBERTY 2,098,055

PUG MILL ATTACK OF TITANIFEROUS ORES l0 Paddle Blade II Spacer Collars l Paddle Shufl Filed Nov. 23, 1935 l3 Discharge Chute For Finished Product l2 Mixer Shell E INVENTOR.

F. H. McB ERTY.

ATTORNEY Patented Nov. 2, 1937 v 2,098,055 rue MILL ATTACK or 'rrrnmmnous ones Ford H. McBerty, Newark, Del., assignor, by

mesne assignments, to E. I. du Pont de Nemours and Company, a corporation of Delaware Application November 23,1935, Serial No. 51,248

The present invention relates to processes in which a titaniferous ore is treated withan acid to recover the titanium values of said ore in a water soluble form.

More particularly this invention relates to processes where a titanium ore and an acid of suitable strength is continuously fed into a reaction zone where the mixture is submitted to vigorous agitation and where the reacting mixture is moved away from the zone of feeding to a zone where the reaction is completed, and where the-reacted material is continuously discharged as a solid, disintegrated mass; the invention comprises effecting such movement of the reacting masses by means of a plurality of helicoidal screw conveyors acting in parallel at diiferent speeds.

In an application by J. E. Booge, I. J. Krchma, and R. M. McKinney, Ser. No. 51,254, filed on even date herewith for: Process of recovering soluble titanium compounds from titaniferous ores, a process is disclosed in which a titanium ore and an acid are continuously fed into a zone in which the reaction between said acid and ore is initiated; the resulting hot pasty mass is moved away from said initial zone into a second zone in which it is kept under agitation and moved forward while the reaction continues, and the reaction mass is finally discharged as a solid disintegrated mass. One characteristic of operating in this manner is that the reaction mass at one stage of the reaction does not come in contact with or is mixed with other parts of the reaction mass which has not reached the same stage of reaction.

Many technical difliculties arise in operating in this manner and these difliculties are overcome in my invention according to which I treat the reaction mass of ore and acid in a conveyor type of apparatus in which I move the reaction mass by means ofv a plurality of parallel helicoidal screws which rotate at diflerent speeds.

The attached drawing shows in a diagrammatical manner a conveyor type apparatus with two helicoidal screws suitable for use in the reaction of sulfuric acid and ilmenite according to my invention.

(I) and (2) represent paddle shafts which are driven at slightly different speeds by intermeshing gears (I5) and (ii), of which thelatter is driven by large gear (I1) driven in turn by pinion (I8) and shaft (I9). Shaft (I) is carried in end bearing (8) labyrinth thrust bearing (4) and end bearing (5). Shaft (2) is carried in end bearing (6) labyrinth thrust bearing (1) 5 andend bearing (I). Between bearings (I) and (4), and (6) and ('l) 'is the mixer shell (I2), in the bottom of which is discharge chute opening (I3). The inside vertical cross section of the shell consists of arcs of circles drawn about the center lines of shafts (I) and (2) intersecting along line (I I) and extended vertically upwards at the side walls. Inside the shell (I2) the shafts carry case steel collars (9) on which are formed paddle blades (I0) alternating with spacer collars (I I). These paddles are arranged to propel m material from the drive end of the conveyor to the discharge chute opening (I3). The length of the paddles (I0) is such as to clear shells (I2) as they revolve, and alsothe adjacent collars by about 1".

In operating my novel process I, for instance, provide a mixing tank ahead of the double screw conveyor. A predetermined amount of oleum is introduced into this tank and the agitator started, ore is then introduced into the tank and a mixture of predetermined composition produced. Oleum and ore are then continuously introduced into the mixer at the correct ratio, and such mixture allowed to overflow into the feed end of the screw conveyor, the rotation of which has been started. Simultaneously with this acid-ore mixture, I feed into the conveyor an amount of water or dilute acid, such as is for instance obtained in the hydrolysis of a titanium sulfate solution, the amounts of such diluent, its strength, and temperature being such that upon comple tion of the reaction a solid disintegrated mass is obtained.

As soon as the oleum-ore mixture and the dilu-' ent begin flowing into the reaction conveyor, heat 35 is developed and the exothermic reaction between the acid and ore is initiated. The mass progresses further and gradually thickens as the reaction proceeds. This thickening and solidifying of the reaction mass causes most of the difliculties enumerated in previous manners of operation, In my novel type of process I find that caking of the mass is prevented by. the fact that, due to the difference in speed of the paddle shafts, the paddles on either shaft scrape the entire periphery of the adjacent shaft collar and knock oif any large masses of material tending to build up on adjacent paddles. I

The temperature gradually increases during reaction, but due to constant agitation and the progressive movement of the mass the heat is easily disseminated, and no. local overheating takes place. The temperature can easily be controlled by varying the speed of the rotation of the paddle shafts, and by varying the amount of diluent c5 erations are obtained whenth'e mass is allowed to.

added to the oleum-ore mixture. The best op the reaction by maintaining the feed end of the apparatus at sufilciently high temperature.

The operations in the screw conveyor are preferably conducted in such a manner that the reaction is substantially completed when the dry 7 mass emerges from the apparatus. If it is desired to increase the output of the conveyor, I can also operate in such a manner that the conversion is only carried out to about where the massis already solid. The reaction is then completed by maintaining the mass at elevated temperatures for a few hours, and this can easily be done by feeding the mass into a heated rotary kiln of any desired type.

The following examples will illustrate the operations according to my novel process. It will be understood that the amounts, concentrations of acid, ore, and temperature conditions under which I operate are well known in this art, and that the novelty in my process relates particularly to the mechanical handling of the reaction mass during the action of the acid upon the ore.

Example I The reaction was carried out in a reaction conveyor, 12 feet long, 3 feet wide, 2 feetdeep, having .two 6 inch shafts on 15 inch centers equipped with 19 paddles each and rotating inwardly at 14 R- P. M. and 15 R. P. M. respectively. The paddles were 18 inches over all with a pitch of to the axis of the shaft. These shafts were driven through suitable gears from the feed end by means of a 30 horsepower motor with a 10 inch belt. The motor was connected directly across the line with no relays or starting equipment and with a watt meter interconnected to indicate power consumption.

The mixing tank was of steel, 40 inches inside diameter and 4 feet deep, and was mounted on a platform scale. Mixing was provided by a 5 horsepower rapid mixer with a single 8 inch propeller of steel. The overflow to the mill was through a 4 inch steel pipe near the top and protected on the inside bya baflle.

In this run, the operation of the equipment is the same as that already disclosed. The ilmenite used comprised approximately 53% TlQz, 25% FeO, and 14% FezOa. This was finely ground and was added to the mixing tank at a rate of 3,340 pounds per hour (40 tons/day). The oleum used was 104 H2804 and was fed to the mixing tank at a rate of about 5000 lbs. per hour. This rate was accurately determinable by careful calibration of the oleum orifice.

The reaction was started by the addition of water to the oleum-ore mixture in the conveyor. When the reaction started the switch was made to dilute acid, admitted at a rate of about 1800 pounds per hour. The composition of the dilute acid was 23-25% free H2804 and 8 grams per liter of soluble titanium expressed as T102. The rate of dilute acid addition was varied over a comparatively narrow range in order to control the reaction and to produce a satisfactory mass. The

as percent H2804; (4) conversion of the titanium content of the ilmenite ore to a soluble form expressed as percent.

Percent Percent Percent Percent Example II The ilmenite usedin this run was the same as given in Example I and was added to the mixing tank at a rate of about 4100 pounds per hour. The oleum used was 104% H2804 and was fed to the .tank at a rate of approximately 6000 lbs. per hour. The dilute acid used, as in the previous case, was at a rate of about 2300 lbs. per hour.

The run was allowed to proceed for 19 hours while four composite samples of the decomposed mass were taken. The total quantity of soluble titanium, expressed as T102, produced was 17.6 tons.

The results obtained from the analysis of the mass are given below: (1) amount of soluble titanium expressed as percent TiOz; (2) amount of ferrous and ferric sulfates expressed as percent Fe; (3) amount of sulfuric acid combined with the Ti and Fe plus any excess present, expressed as percent H2804; (4) conversion of the T1 to the.

soluble form, expressed as percent.

Percent Percent Percent Percent- 17. 1 10. e 61. 1 s7. 1 17.3 10.9 01.9 86.1 17.4 10.8 58.7 87.2 16. a 10. s 57. 2 77. 5

any mineral containing titanium in a form amenable to attack by an acid. I am not limited to one particular size of ore but can decompose rather coarse material, such as ilmenite sand, both conveniently and economically.

The oleum to be pre-mixed with the ilmenite ore does not have to be 104% H7804, but is only limited to those values that will permit the reaction to take place in the conveyor; However,

104% acid was found to give the easiest operating conditions.

The temperature of the ore-oleum mixture is not important as long as it does not rise high enough to initiate the reaction in the mixing tank rather than in the conveyor. Of course, with more dilute acid, this temperature can safely be maintained somewhat higher.

While I prefer to use weak dilute waste acid to initiate and maintain the reaction temperature for reasons of economy, water or steam will produce the same results with good control and with the added advantage that the concentration of the primary acid does not have to be as high.

The speed of the revolving paddles in the reaction conveyor does not necessarily have to be 14 and 15 R. P. M. It is only important to have them at slightly difierent speeds in order to aid the passage of the material through the length and also to prevent the clogging of the conveyor.

The advantages and improvements of my hereinbefore disclosed invention can be readily seen from the described operation and results obtained, and are briefly listed below:

(1) The steady and uniform feeding of ore and oleum; (2) the use of weak acid that is a byproduct of the subsequent treatment; (3) the continuous and automatic method of maintaining the reaction temperature after it has been started; (4) the continuous supply of a product in a form suitable for curing; (5) the subsequent uniform rate of finished product with conversions of the TiOz as high as 94.5 to 95.5%. To elaborate further for emphasis, the advantages can be divided into two main divisions. The first of these is the continuous and uniform product with close to 100% conversion of the titanium oxide and the second is the automatic nature of the process necessitating very little supervision and practically no manual labor.

I claim:

1. In a process for treating'titaniferous ore with sulfuricacid to recover a water soluble titanium compound in solid form which comprises feeding said ore and acid of suitable strength into a reaction-zone, initiating the reaction between said acid and ore and moving the reaction mixture away from the zone where the reaction is initiated and. keeping the reaction mixture moving until it is discharged in a solid disintegrated form, the step of effecting said movement in said reaction zone by means of a plurality of adjacent and cooperatively acting helicoidal parallel screws rotating at different speeds and adapted to prevent substantial accumulations of reactant materials on each other.

2. The process of claim 1 in which said acid is strong sulfuric acid, said ore is ilmenite and said reaction zone is a substantially horizontal trough in which two adjacent and cooperatively acting parallel, horizontal screws are rotated at diflerent speeds.

3. In a process for treating titaniferous ores with sulfuric acid and wherein the mass being treated isprogressively passed through a zone adapted to initiate and complete the desired reaction therebetween, the step of effecting progressive movement of said mass through said zone by means of a plurality of adjacently associated and cooperatively-acting, helical screws rotating at different speeds and provided with means for preventing substantial accumulations of reactant materials on a coacting screw.

4. In a process for treating titaniferous ores with sulfuric acid, wherein the ore-acid mass under treatment is progressively passed through a zone adapted to initiate and complete the desired reaction therebetween, the step of effecting such progressive movement of said mass by means of a plurality of cooperatively-acting, helical, parallel screws rotating at different speeds and provided with adjacently associated means for removing and preventing any substantial accumulation of reactant materials on an associated parallel screw.

5. The process of claim 4 in which the acid employed is strong sulfuric, the ore is ilmenite, and the reaction zone comprises a substantially horizontal trough in which two adjacent and cooperatively-acting, parallel, horizontal screws are rotated at difierent speeds.

6. In a process for treating titaniferous ores with sulfuric acid and wherein the mass of ore and acid being treated is progressively passed through a reaction zone adapted to initiate and complete the desired reaction, the step of effecting progressive movement of said mass by means of a plurality of cooperatively-acting, helical, parallel screws rotating at different speeds, said screws being provided with adjacently associated paddles and collars in such operative relationship with respect to each other as to remove and prevent any substantial accumulation of reactant materials on an associated screw.

7. In a process for treating titaniferous ores with sulfuric acid to recover a water-soluble titanium compound in solid form which comprises feeding said ore and acid of suitable strength into a reaction zone, initiating the desired reaction between said acid and ore by means of an aqueous diluent, progressively moving the reaction mixture away from the zone of reaction initiation, and subsequently discharging the reaction mixture on completion of treatment in solid, disinte rated form, the step of efiecting said progressive movement by means of a plurality of cooperatively-acting, helical, parallel screws rotating at different speeds, said screws being provided with adjacently associated paddles and collars in such operative relation with respect to each other as to remove and prevent any substantial accumulation of the re actant material on an associated paddle or collar.

8. A process for treating a titanium containing ore, comprising progressively feeding said ore, together with sulfuric acid, into a reaction zone and effecting progressive movement of said mass through said zone by means of a plurality of adjacently associated and cooperatively acting, helical screws rotating at different speeds and provided with means for preventing substantial accumulation of reactant materials on an associated screw.

FORD H. McBERTY. 

